1. Field of the Invention
The present invention relates to an optical disc having a minute integrated circuit (IC) memory chip, called an IC tag or an RF tag, which stores a variety of readable data and which has a radio communication function.
2. Description of the Related Art
In recent years, various minute IC memory chips having radio communication functions have been put to practical use. Optical discs, such as compact discs (CDs) or digital versatile disks (DVDs), each having such a minute IC memory chip and an antenna coil, have been proposed. A variety of management data, which is stored in the minute IC memory chip, is applied to various purposes.
In the applications of such a minute IC memory chip, for example, a unique identification (ID) provided for the disc is helpful to management of the disc or prevention of theft of the disc. Providing the disc with a writable memory that can record a variety of information allows accounting or right information of content, data, or files to be stored. In addition, provision of a private key permits authentication by, for example, public key infrastructure (PKI) in a processing circuit including a CPU to provide a decryption key of encrypted content, data, or files only to a legal party or to provide a security function, for example, to allow the accounting or right information to be updated.
Accordingly, since the information stored in such an IC memory chip cannot easily correspond to the data or content in the optical disc if the information in the IC memory chip is separated from the optical disc, it is preferable that the IC memory chip be integrated with the optical disc.
A known CD on which such a minute IC memory chip is integrally mounted is disclosed in Japanese Unexamined Patent Application Publication No. 2001-210057.
FIG. 7A is a plan view showing the structure of a known CD and FIG. 7B is a cross-sectional view of the CD in FIG. 7A. FIG. 8A is a plan view showing the structure of the CD shown in FIGS. 7A and 7B, which has an IC memory chip and an antenna coil mounted thereon. FIG. 8B is a cross-sectional view of the CD in FIG. 8A.
Referring to FIGS. 7A and 7B, a CD 100 has a transparent base 110 made of, for example, polycarbonate, a signal recording surface 111 that is a series of pits, and a reflective film 120 made of aluminum or the like. The signal recording surface 111 is formed on the top surface of the base 110 and the reflective film 120 is formed on the signal recording surface 111. A protective film 130 made of a resin is formed on the reflective film 120.
A center portion 140 to which a disk chuck (not shown) fits is provided around the center of the CD 100. The overall thickness of the CD 100 is defined to be a value around 1.2 mm.
The CD 100 is irradiated with a light beam 160 from the transparent base 110 side. Signals on the series of pits are read by the light reflected from the reflective film 120.
In the CD 100, it is difficult to provide the IC memory chip and the antenna coil described above in a recording area in the transparent base 110 through which the light beam is transmitted. In addition, since the reflective film 120 and the protective film 130 have a small thickness, it is also difficult to embed the IC memory chip and the antenna coil in these films. Hence, the IC memory chip and the antenna coil are provided, for example, on a surface opposing a reproducing surface for the disc in the center portion 140, as shown in FIGS. 8A and 8B. That is, referring to FIGS. 8A and 8B, a minute IC memory chip 170 is provided on the surface opposing the reproducing surface for the disc in the center portion 140, and an antenna coil 180 is annularly provided along the inside perimeter of the center portion 140. The antenna coil 180 passes through the minute IC memory chip 170. The bottom surface of the CD 100 serves as a reproducing surface 100A for the disc and the top surface of the CD 100 serves as a reproducing surface 100B for the chip.
A known DVD on which such a minute IC memory chip is integrally mounted is disclosed in Japanese Unexamined Patent Application Publication No. 9-245381.
FIG. 9A is a plan view showing the structure of a known DVD and FIG. 9B is a cross-sectional view of the DVD in FIG. 9A. FIG. 10A is a plan view showing the structure of the DVD shown in FIGS. 9A and 9B, which has an IC memory chip and an antenna coil mounted thereon. FIG. 10B is a cross-sectional view of the DVD in FIG. 10A.
Referring to FIG. 9B, a DVD 200 has two transparent bases 210 and 220 made of, for example, polycarbonate and an adhesive layer 230 made of an adhesive resin, which is sandwiched between the transparent bases 210 and 220. Signal recording surfaces 211 and 221 each being a series of pits are formed inside the transparent bases 210 and 220, respectively. A reflective film 240 made of aluminum or the like is formed on the signal recording surface 211 and a reflective film 250 made of aluminum or the like is formed on the signal recording surface 221.
The overall thickness of the DVD 200 is defined to be a value around 1.2 mm.
The DVD 200 is irradiated with a light beam 280 from both the transparent base 210 side and the transparent base 220 side. Signals on the series of pits are read by the light reflected from the reflective films 240 and 250.
It is difficult to provide the IC memory chip and the antenna coil described above in a recording area of information in the DVD 200 and the DVD 200 has no center portion, unlike the CD 100 shown in FIGS. 7A and 7B. Hence, for example, as shown in FIGS. 10A and 10B, a minute IC memory chip 290 and an antenna coil 300 are embedded in the joint of the transparent bases 210 and 220 at the center of the DVD 200. That is, the minute IC memory chip 290 is provided near the center portion of the DVD 200 and the antenna coil 300 is annularly provided so as to be concentric with the DVD 200. The antenna coil 300 passes through the minute IC memory chip 290.
The bottom surface of the DVD 200 serves as a reproducing surface 200A for the disc and the top surface of the DVD 200 serves as a reproducing surface 200B for the chip in FIG. 10B.
As described above, in known optical discs, the IC memory chip or the antenna coil must be selectively provided in a limited area in view of the relationship with a light transmission area or conditions of the film thickness. Hence, known optical discs are likely to have restrictions on the size of elements or functions thereof and they have disadvantages in their design and manufacturing.